I was just remembering the O.S. .60 I soaked in jewelry cleaner...
I have a vibrating (not quite ultra-sonic ) cleaner for jewlery / silverware that came with a quart bottle of this blue liquid that smells like home permanant solution my mom and sisters used to use. I think it has peroxide in it? Anyway...the O.S. has a similar gray color to it now, almost the same as your Webra, but a "flat" gray...

That was the first and last engine I did in that cleaner...now I stick with the crock pot 'o antifreeze.

That jewlery cleaner does clean surface rust off of steel parts like cranks, bearings, etc. very well though.